There are numerous situations in which it is necessary to pump a mixture of fluids from two different sources. Commonly, it is desirable to control the proportions of the mixture and to achieve thorough and uniform mixing of the fluids as they are pumped.
This type of two fluid mixing occurs in many environments. One common situation involves the mixing of soluble oil in water for use as a cooling fluid or a hydraulic fluid. The presence of oil has a corrosion-inhibiting effect. A ratio of 95 parts water to 5 parts oil is typical.
One known arrangement for pumping and mixing such fluids employs two pumps, with the mixing taking place downstream. It is, however, difficult to maintain the selected mixture proportion because the speed at which each pump operates will vary with the instantaneous resistance that it meets. Maintaining the proper adjustment as to the relative speeds of the pumps can become very difficult, particularly if the speeds of the pumps are to be varied from time to time. Moreover, the downstream mixing of the fluids may require additional components that impede the fluid flow and increase the resistance to pumping, even if the two pumps are mechanically connected by gears or otherwise to ensure the desired speed ratio.
An objective of the present invention is to provide a simple reliable mixing pump in which the proportion of two fluids being pumped and mixed remains constant and is independent of the aggragate rate at which the mixture is pumped. Another objective is to provide such a pump in which the fluids are thoroughly mixed as they are pumped. A still further objective is to supply a substantially even, pulse-free flow of the mixed fluids at any desired outlet pressure.